TweetFollow Us on Twitter

September 95 - MPW Tips and Tricks: Customizing Source Control With SourceServer

MPW Tips and Tricks: Customizing Source Control With SourceServer

Tim Maroney

When two engineers on a team edit the same source file at the same time, the resulting chaos can be terrible to behold. Source control was invented to mitigate the problem. Most Macintosh programmers are familiar with the MPW Shell's Check In and Check Out dialogs, and with its Projector commands. The next frontier of custom source control involves SourceServer, a nearly faceless application that implements most of the Projector commands. MPW scripts are easy to write, but they're no match for the power, speed, and friendliness of compiled software. SourceServer exports Projector commands as Apple events, allowing source control from compiled software without launching the MPW Shell in all its pomp and splendor.

Popular third-party development environments often send Apple events to SourceServer for integrated source control. You can also use SourceServer to customize Projector beyond what you might have thought possible. For instance, you can drag source control, kicking and screaming, into the modern world of user experience with drop-on applications. In this column, I'll show you how to check a file in or out with a simple drag and drop, and how to use SourceServer for other things as well. The sample code is provided on this issue's CD; SourceServer is distributed, with documentation, on the MPW Pro and E.T.O. CDs (available from Apple Developer Catalog) and with third-party development systems.

APPLE EVENTS FOR SOURCESERVER

Apple events have many faces, but they're primarily a way of communicating between different applications.

Each Apple event encapsulates a message as a command with any number of input parameters; the receiver of the message may return any number of result parameters to the sender. The most basic unit of data is the Apple event descriptor, which consists of a type code and a data handle. Apple events are built out of descriptors and are themselves special kinds of complex descriptors.

    For an excellent introduction to Apple events, see "Scripting the Finder From Your Application" by Greg Anderson in develop Issue 20.*

SourceServer's commands are represented as descriptor lists. Its Apple events are exact duplicates of the MPW Shell's Projector commands, but to avoid the overhead of a full command parser, both the command name and each argument are descriptors in the descriptor list. This saves you the trouble of putting quotes and escapes into arguments that might contain spaces or other special characters. The downside is that you have to expand arguments yourself: you can't pass in MPW wildcard characters, backquoted commands for expansion, or other special constructs.

Creating descriptor lists may sound harder than writing MPW scripts, but that's only because it is. I've provided some utility routines to ease the way, though. Listing 1 shows the utilities and illustrates how to make a command to check out a file for modification. As illustrated in the CheckOut routine in this listing, you call the CreateCommand routine first and then use the AddXArg routines to add arguments.

Listing 1. Creating SourceServer commands

OSErr CreateCommand(AEDesc *command, CString commandText)
// Begin a new SourceServer command; name of command is in
// commandText.
{
   OSErr err = AECreateList(NULL, 0, false, command);
   if (err != noErr) return err;
   err = AddCStringArg(command, commandText);
   if (err != noErr) (void) AEDisposeDesc(command);
   return err;
}

OSErr AddCommentArg(AEDesc *command, StringPtr comment)
/* Add a "-cs comment" argument to a SourceServer command. */
{
   OSErr err;
   if (comment[0] == 0) return noErr;
   err = AddCStringArg(command, "-cs");
   if (err != noErr) return err;
   err = AddPStringArg(command, comment);
   return err;
}

/* Other SourceServer argument utilities */
OSErr AddDirArg(AEDesc *command, short vRefNum, long folderID);
OSErr AddProjectArg(AEDesc *command, StringPtr projectName);
OSErr AddUserArg(AEDesc *command, StringPtr userName);
OSErr AddFullNameArg(AEDesc *command, FSSpec *file);
OSErr AddPStringArg(AEDesc *command, StringPtr string);
OSErr AddCStringArg(AEDesc *command, CString string);

OSErr CheckOut(FSSpec *file, StringPtr userName,
               StringPtr projectName, StringPtr comment)
/* Create a "Check Out Modifiable" command for SourceServer: */
/* CheckOut -m -cs <comment> -d <dir> -project < */
/*           project> -u <user> <file> */
{
   OSErr             err;
   AEDesc          command;
   CStringHandle    output = NULL, diagnostic = NULL;

   err = CreateCommand(&command, "CheckOut");
   if (err != noErr) return err;
   err = AddCStringArg(&command, "-m");
   if (err == noErr) err = AddCommentArg(&command, comment);
   if (err == noErr)
     err = AddDirArg(&command, file->vRefNum, file->parID);
   if (err == noErr) err = AddProjectArg(&command, projectName);
   if (err == noErr) err = AddUserArg(&command, userName);
   if (err == noErr) err = AddPStringArg(&command, file->name);
   if (err == noErr)
     err = SourceServerCommand(&command, &output, &diagnostic);
   (void) AEDisposeDesc(&command);
   /* Display output or diagnostic text as desired. */
   if (output != NULL) DisposeHandle((Handle) output);
   if (diagnostic != NULL) DisposeHandle((Handle) diagnostic);
   return err;
}

Some of the utilities take Pascal strings, while others take C strings, which could well be considered bad programming practice. I chose this dubious method not because I'm on drugs, but because Pascal strings and C strings are used in different ways. SourceServer's text descriptors are C strings; when passed to these utilities as string constants, they shouldn't be converted from Pascal format in place, since some compilers put constants in read-only areas. If you're internationally savvy, you may have another objection: string constants themselves are bad practice. However, for better or worse, MPW scripts and tools are not internationalized. Just like aliens in Star Trek, all MPW programmers are assumed to speak English.

While on the subject of programming practice, I must gently reprimand SourceServer for its approach to Apple events, in which script commands are simulated through a single 'cmnd' event. SourceServer's idiosyncratic convention dates from the earliest days of Apple events, and modern guidelines discourage this type of design. An application implementing its own Apple events should designate a different command code for each operation, treating arguments as keyword parameters.

Listing 2 shows how to send an Apple event to SourceServer. It's first necessary to find and perhaps launch the SourceServer application. The snippet called SignatureToApp (by Jens Alfke) on this issue's CD accomplishes this with a single function call. Simply pass in the creator code of SourceServer, which is 'MPSP'.

Listing 2. Sending commands to SourceServer

OSErr SourceServerCommand(AEDesc *command, CStringHandle *output,
                          CStringHandle *diagnostic)
{
   AppleEvent            aeEvent;
   AERecord              aeReply;
   AEDesc                sourceServerAddress, paramDesc;
   ProcessSerialNumber   sourceServerProcess;
   /* SignatureToApp requires this due to a minor bug */
   FSSpec                appSpec;
   long                  theLong, theSize;
   DescType              theType;
   OSErr                 err;

   *output = *diagnostic = NULL;   /* default replies */
   
   /* Find the SourceServer process and make a descriptor for its */
   /* process ID. */
   err = SignatureToApp('MPSP', NULL, &sourceServerProcess,
                         &appSpec, NULL, Sig2App_LaunchApplication,
                         launchContinue + launchDontSwitch);
   if (err != noErr) return err;
   err = AECreateDesc(typeProcessSerialNumber,
                      (Ptr) &sourceServerProcess,
                     sizeof(ProcessSerialNumber),
                     &sourceServerAddress);
   if (err != noErr) return err;

   /* Create and send the SourceServer Apple event. */
   err = AECreateAppleEvent('MPSP', 'cmnd', &sourceServerAddress,
                           kAutoGenerateReturnID, kAnyTransactionID,
                           &aeEvent);
   /* done with the address descriptor */
   (void) AEDisposeDesc(&sourceServerAddress);
   if (err != noErr) return err;
   /* add the command */
   err = AEPutParamDesc(&aeEvent, keyDirectObject, command);
   if (err != noErr) { (void) AEDisposeDesc(&aeEvent); return err; }
   err = AESend(&aeEvent, &aeReply,
                kAEWaitReply + kAENeverInteract, kAENormalPriority,
                kNoTimeOut, NULL, NULL);
   (void) AEDisposeDesc(&aeEvent);   /* done with the Apple event */
   if (err != noErr) return err;

   /* Check for an error return in the keyErrorNumber parameter. */
   err = AEGetParamPtr(&aeReply, keyErrorNumber, typeInteger,
                      &theType, &theLong, sizeof(long),
                      &theSize);
   if (err == noErr && (err = theLong) == noErr) {
      /* Get the standard output from the keyDirectObject parameter. */
      err = AEGetParamDesc(&aeReply, keyDirectObject, typeChar,
                           &paramDesc);
      if (err == noErr)
          *output = (CStringHandle) paramDesc.dataHandle;
      /* Get the diagnostic output from the 'diag' parameter. */
      err = AEGetParamDesc (&aeReply, 'diag', typeChar,
          &paramDesc);
      if (err == noErr)
          *diagnostic = (CStringHandle) paramDesc.dataHandle;
      /* Get the MPW status from the 'stat' parameter -- it */
      /* becomes our error return. */
      err = AEGetParamPtr(&aeReply, 'stat', typeInteger,
                         &theType, &theLong,
                         sizeof(long), &theSize);
      if (err == noErr) err = theLong;
   }

   /* done with the reply descriptor */
   (void) AEDisposeDesc(&aeReply);
   return err;
}

The event must be created before it can be sent. For SourceServer, there's a single parameter, named keyDirectObject, which is the descriptor list containing the command. After sending the event, you must extract the results. The results of an Apple event are returned as keyword parameters in a reply descriptor. First there's the standard keyErrorNumber parameter, which returns an error code if delivery failed. SourceServer returns three other parameters: The 'stat' parameter contains a second error code; if it's nonzero, SourceServer tried to execute the command and failed. When there's an error, there will be diagnostic output in the 'diag' parameter, a handle containing text from the MPW diagnostic (error) channel. Finally, there's standard output -- a handle specified by keyDirectObject -- which contains explanatory text.

PROJECTDRAG -- DRAG AND DROP SOURCE CONTROL

The Macintosh has always had a drag and drop user experience, but the true power and generality of dragging has been widely recognized only recently. The drag paradigm can even be used for source control. To turn Projector into a drag-savvy system, I've written a set of utilities called ProjectDrag (source code and documentation are provided on this issue's CD). You simply drag and drop icons onto the following miniapplications that make up ProjectDrag, and the corresponding function is performed:
  • Check In and Check Out, for checking files in and out

  • ModifyReadOnly, for editing a file without checking it out

  • Update, for bringing a file or folder up to date, as well as canceling checkouts and modify-read-only changes

  • ProjectDrag Setup, for configuring the system
These utilities are based on a drop-on application framework called DropShell (written by Leonard Rosenthol and Stephan Somogyi), also on the CD. When a file is dropped onto an application, the application receives an Open Documents ('odoc') event. DropShell takes care of the rigmarole of receiving this and other required Apple events. The ProjectDrag miniapplications pull the file specifications out of 'odoc' events and create SourceServer commands that operate on the files and folders that were dropped on their icons.
    DropShell is also available on the Internet at ftp://ftp.hawaii.edu/pub/mac/info-mac/Development/src/ and at other Info-Mac mirror sites.*
Some setup is required. ProjectDrag needs to know the locations of Projector databases. It maps between project names and Projector database files by keeping aliases to database folders in its Preferences folder. To start using a project, simply drag its ProjectorDB file or the enclosing folder onto ProjectDrag Setup. Projector also needs to know your user name, and your initials or a nickname are used in change comments at the start of files. These are stored in a text file in the Preferences folder. ProjectDrag asks you for this information if it can't find it, or you can launch ProjectDrag Setup and give the Set User Name command.

ProjectDrag is scriptable, unlike SourceServer and the MPW Shell. The miniapplications have an Apple event terminology resource ('aete') to advertise their events to scripting systems. This allows you to add source control commands to any application that lets you add AppleScript scripts to its menus.

ProjectDrag is able to run remotely over a network. This circumvents a limitation of SourceServer, which can only be driven locally. ProjectDrag can receive remote Apple events and then drive a copy of SourceServer that's local to it. Among other uses, this could support an accelerator for Apple Remote Access. Checking a file in or out over ARA takes a few minutes, which is fine, especially for those who find tedium particularly enjoyable. Copying files is faster. With local AppleScript front ends for remote ProjectDrag miniapplications, you could copy files to and from a remote "shadow folder" and initiate SourceServer commands at the remote location, where they would execute over a fast network such as Ethernet.

I like to think that I can solve user interface problems in my sleep. When I was writing ProjectDrag, I had a dream of a better user experience. Instead of miniapplications, ProjectDrag would be a magical system extension that would put a single small icon at some convenient place on the screen. When you dragged a file onto this icon, it would pop open into a temporary window and show you icons for the various options. Dreams are great for creativity, but it's easier to weigh alternatives when you're awake. After I woke up, I realized that miniapplications will be able to do the same thing.

Here's how: In Copland, the next generation of the Mac OS, the Finder will spring-load folders so that they open automatically when you drag onto them. It will also let you stash commonly used folders at the bottom of the screen, where they appear as short title bars. Drag the ProjectDrag folder to the bottom of the screen and you're set! Since the Finder will be providing my dream interface, there's no point in a lot of trap patching and extensibility infrastructure to accomplish the same thing.

Copland will bring another user experience benefit to ProjectDrag: it's planned that document windows will have a draggable file icon in their title bar, so you'll be able to use ProjectDrag on an open document by dragging the icon from its window.

YOU TAKE IT FROM HERE

You can create programs that use SourceServer for many other tasks. On cross-platform projects, Projector is sometimes used to control both platforms' source folders. This can lead to baroque and error-prone processes. With SourceServer, you can create front ends that do the right thing. They could copy to remote folders over a network, or lock read-only files since the other platform doesn't see Projector's 'ckid' resources.

Quality is an interesting area for source control applications. A quality tool could query Projector databases for the frequency and scope of changes at various stages of the project, correlating them with bug tracking to develop project metrics. Along similar lines, a tool could measure the change rate of various files to assist in what the quality gods refer to as root-cause analysis.

SourceServer is much more than a way for development systems to provide integrated source control. It's great for structuring your internal development process as well!

TIM MARONEY wrote TOPS Terminal and BackDrop, and has been a major contributor to TOPS for Macintosh, FaxPro, and Cachet. He has also contributed to Fiery, the Disney Screen Saver, Ofoto, Colortron, and the Usenet Mac Programmer's Guide. Tim learned computer networking while working on the Andrew and MacIP projects at Carnegie Mellon and studied compiler design in graduate school at Chapel Hill. He has written for all three major operating systems and a few minor ones. On the Macintosh, Tim's code has included applications, INITs, control panels, HyperCard stacks, XCMDs, shared libraries, trap patches, plug-ins, scripts, and things more difficult to characterize. Tim is currently doing contract work at Apple, and is available for parties and special events at a nominal cost.*

Thanks to Greg Anderson, Arno Gourdol, and B. Winston Hendrickson for reviewing this column.*

Special thanks to Jens Alfke, Jon Pugh, Leonard Rosenthol, and Stephan Somogyi.*

 
AAPL
$97.67
Apple Inc.
+0.64
MSFT
$44.50
Microsoft Corpora
+0.10
GOOG
$589.02
Google Inc.
-4.33

MacTech Search:
Community Search:

Software Updates via MacUpdate

TinkerTool 5.3 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Audio Hijack Pro 2.11.0 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Autopano Giga 3.6 - Stitch multiple imag...
Autopano Giga allows you to stitch 2, 20, or 2,000 images. Version 3.0 integrates impressive new features that will definitely make you adopt Autopano Pro or Autopano Giga: Choose between 9... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more

Latest Forum Discussions

See All

Jacob Jones and the Bigfoot Mystery : Ep...
Jacob Jones and the Bigfoot Mystery : Episode 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Jacob Jones is back in Episode 2 of one of Apples 'Best of 2013' games and an App Store... | Read more »
New Trailer For Outcast Odyssey, A New K...
New Trailer For Outcast Odyssey, A New Kind of Card Battler Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Out this Fall is a new kind of card battle game: Outcast Odyssey. | Read more »
Garfield: Survival of the Fattest Coming...
Garfield: Survival of the Fattest Coming to iOS this Fall Posted by Jennifer Allen on July 25th, 2014 [ permalink ] Who loves lasagna? Me. Also everyone’s favorite grumpy fat cat, Garfield. | Read more »
Happy Flock Review
Happy Flock Review By Andrew Fisher on July 25th, 2014 Our Rating: :: HERD IT ALL BEFOREUniversal App - Designed for iPhone and iPad Underneath the gloss of Happy Flock’s visuals is a game of very little substance. It’s cute, but... | Read more »
Square Register Updates Adds Offline Pay...
Square Register Updates Adds Offline Payments Posted by Ellis Spice on July 25th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Looking For Group – Hearthstone’s Curse...
For the first time since its release (which has thankfully been a much shorter window for iPad players than their PC counterparts), Blizzard’s wildly successful Hearthstone: Heroes of Warcraft CCG is sporting some brand new content: the single... | Read more »
Poptile Review
Poptile Review By Jennifer Allen on July 25th, 2014 Our Rating: :: SIMPLY FUNUniversal App - Designed for iPhone and iPad Simple yet a little bit glorious, Poptile is a satisfying entertaining puzzle game with oodles of the ‘one... | Read more »
Modern Combat 5: Blackout Review
Modern Combat 5: Blackout Review By Brittany Vincent on July 25th, 2014 Our Rating: :: LESS QQ, MORE PEW PEWUniversal App - Designed for iPhone and iPad The fifth entry into the blockbuster Modern Combat series is what mobile... | Read more »
Watch and Share Mobile Gameplay Videos W...
Watch and Share Mobile Gameplay Videos With Kamcord Posted by Jennifer Allen on July 25th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
THE KING OF FIGHTERS '98 (Games)
THE KING OF FIGHTERS '98 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: Series’ masterpiece “KOF ’98” finally joins the battle on iPhone! FEATURES:■ The best game balance in the “KOF”... | Read more »

Price Scanner via MacPrices.net

iMacs on sale for $150 off MSRP, $250 off for...
Best Buy has iMacs on sale for up to $160 off MSRP for a limited time. Choose free home shipping or free instant local store pickup (if available). Prices are valid for online orders only, in-store... Read more
Mac minis on sale for $100 off MSRP, starting...
Best Buy has Mac minis on sale for $100 off MSRP. Choose free shipping or free instant local store pickup. Prices are for online orders only, in-store prices may vary: 2.5GHz Mac mini: $499.99 2.3GHz... Read more
Global Tablet Market Grows 11% in Q2/14 Notwi...
Worldwide tablet sales grew 11.0 percent year over year in the second quarter of 2014, with shipments reaching 49.3 million units according to preliminary data from the International Data Corporation... Read more
New iPhone 6 Models to Have Staggered Release...
Digitimes’ Cage Chao and Steve Shen report that according to unnamed sources in Apple’s upstream iPhone supply chain, the new 5.5-inch iPhone will be released several months later than the new 4.7-... Read more
New iOS App Helps People Feel Good About thei...
Mobile shoppers looking for big savings at their favorite stores can turn to the Goodshop app, a new iOS app with the latest coupons and deals at more than 5,000 online stores. In addition to being a... Read more
Save on 5th generation refurbished iPod touch...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Many, but not all... Read more
What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Sr. Project Manager for *Apple* Campus 2 -...
…the design and construction of one building or building components of the New Apple Campus located in Cupertino, CA. They will provide project management oversight for Read more
WW Sales Program Manager, *Apple* Online St...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.